1. Chapter 3: The Big Picture: Systems of Change

2. Systems
A system is a set of components or parts that function together to act as a whole.
E.g. Body, city, river
Open system- some energy or material moves into or out of system.
Closed system- no such movements take place.

5. Feedback Feedback is when one part of the system changes
Those changes affect another part of the system
Which affects the first change
Negative feedback- an increase in output leads to a later decrease.
Self-regulating, or stabilizing

6. Feedback
Positive feedback- an increase in output leads to a further increase in the output.
Destabilizing
Environmental damage can be especially serious when peoples use of the environment leads to positive feedback.

7. Positive Feedback

9. Feedback Some situations involve both + and – feedback.
Human pop. in large cities.

10. Stability A stable system is one that
Has a condition that it remains in unless disturbed.
Condition that it returns to if disturbed from it and the cause of the disturbance stops.
Whether this is desirable depends on the system and potential changes.

11. Exponential Growth Growth occurring at a constant rate.
(rather than a constant amount)
Plotted on a graph will form a J shaped curve

13. Exponential Growth Calculating EG involves two related factors
Rate of growth measured as a %
Doubling time in years
Time necessary for the quantity being measured to double.
EG is positive feedback and incompatible w/ sustainability

14. Environmental Unity It is impossible to change only one thing
Everything effects everything else
Earth and its ecosystems are complex entities in which any action may have several or many effects.

15. Environmental Unity: An Urban Example
Many midwestern US cities (i.e. Chicago) have had a shift in land use
Forest or ag land to urban development
Construction increases runoff and soil erosion
Effects river channels and flood hazard
After construction sediment load decreases but runoff still increases
Thus land-use changes set off a series of changes which can trigger additional changes.

16. Environmental Unity: A Forest Example
Forest, stream and fish in the Pacific Northwest
Wood debris form and maintain pool environments in small stream.
Provide rearing habitat for young salmon
Formerly removed because thought to block fish migration
Studying relations between physical and biological systems at the heart of enivor science

18. Uniformitarianism
The physical and biological processes presently forming and modifying Earth are the same now as they were in the past.
A study of past and present processes is key to the future.

19. The beach at Bora Bora is an example of geological short lived landforms –vulnerable to rapped change form storms and other natural processes.

20. Changes and Equilibrium in Systems
Steady state
Input into a system equals output
No net change in the size of the reservoir
Dynamic equilibrium
Because material entering and leaving the systems in equal amounts

21. Changes and Equilibrium in Systems
When input is less than output
The size of reservoir declines
When input is greater than output
The size of the reservoir increases

23. Changes and Equilibrium in Systems
Average residence time- the time it takes for a given part of the total reservoir of a particular material to be cycled through the system. ART= S/F
Large systems w/ a slow rate of transfer of water have a long residence time
Oceans
Difficult to clean up
Contrast to a stream w/ high rate of transfer
Average Residence Time = Amount of anything in reservoir S size of reservoir
Rate at which is added or removed F rate of transfer

24. Average residence time has important implication for environmental systems.
A system such as a small lake with an inlet and an outlet and a high transfer rate of water has a short residence time for water. ART= S(size)/F(rate of transfer)

25. Earth and Life Earth formed 4.6 billion years ago
Life began on Earth 3.5 billion years ago
Since life’s emergence many organisms have evolved, flourished, and become extinct.
Humans too may some day become extinct.
Human activities increase and decrease the magnitude and frequency of natural processes.
Leading to many human caused extinctions.

26. Earth as a Living System
Biota- all living things within a given area
Biosphere- region of Earth where life exists
Also includes the system that sustains life
All living things require energy and materials.
Energy from the sun and interior of Earth
Materials recycles through the system

27. Ecosystem
A community of organisms and its local nonliving environment in which matter cycles and energy flows.
Can be applied to different scales
Puddle to forest to planet
What is common to all is not physical structure but existence of processes
Can be natural or artificial

28. Gaia hypothesis
The hypothesis states that life manipulates the environment for the maintenance of life.
Planet capable of physiological self-regulation
Really a series of hypotheses
Life has greatly affected the planetary environment
Life has altered Earth’s enviro in ways that have allowed it to persist

29. Why Solving Environmental Problems Is Often Difficult
1. Exponential growth
The consequences of EG and its positive feedback can be dramatic, leading to incredible increases of what is being evaluated or measured.

30. Why Solving Environmental Problems Is Often Difficult
2. Lag time
The time between a stimulus and the response of a system.
Long lag time or delays may lead to overshot and collapse
Going beyond the carry capacity can lead to a collapse of a population.

32. Why Solving Environmental Problems Is Often Difficult
3. Irreversible consequences
Consequences that may not be easily rectified on a human scale of decades or a few hundred years.